[PATCH v2 2/3] aarch64: warn if the TME feature is used during assembly.
Richard Earnshaw (foss)
Richard.Earnshaw@arm.com
Mon Jun 29 10:44:24 GMT 2026
On 26/06/2026 16:54, Alice Carlotti wrote:
> On Fri, Jun 26, 2026 at 02:35:15PM +0100, Richard Earnshaw wrote:
>> Arm has obsoleted the unimplemented TME feature. Warn if instructions
>> from this feature are encountered.
>
> We could only use these instruction in assembly if we specify the +tme
> extension, and if we're deprecating the instructions then we should deprecate
> the flag as well. So I think it would be better to emit the deprecation
> warning when parsing the "+tme" extension (and we need only warn about this
> once).
>
I did ponder that approach, but the downside is that it will report problems on Makefiles rather than problems in source code that might be using the feature. That makes it more difficult to focus on files that would need cleaning up as a result of this change (not that I expect there to be many cases).
The +tme option on the command line is harmless unless code is using such instructions.
R.
> Alice
>
>>
>> Also tweak warn_unpredictable_ldst to use const more often, since the
>> arguments are the same as for the new warn_deprecated function.
>> ---
>> gas/NEWS | 4 ++++
>> gas/config/tc-aarch64.c | 24 ++++++++++++++++++++++--
>> gas/testsuite/gas/aarch64/tme-warn.l | 15 +++++++++++++++
>> gas/testsuite/gas/aarch64/tme.d | 1 +
>> include/opcode/aarch64.h | 6 ++++--
>> opcodes/aarch64-tbl.h | 10 +++++-----
>> 6 files changed, 51 insertions(+), 9 deletions(-)
>> create mode 100644 gas/testsuite/gas/aarch64/tme-warn.l
>>
>> diff --git a/gas/NEWS b/gas/NEWS
>> index 4c55a544f25..116d5e62be6 100644
>> --- a/gas/NEWS
>> +++ b/gas/NEWS
>> @@ -1,5 +1,9 @@
>> -*- text -*-
>>
>> +* The aarch64 TME extension has never been implemented in any products. Arm
>> + has withdrawn it from the architecture. The assembler will now warn if
>> + instructions from the extension are detected during assembly.
>> +
>> * The legacy .vtable_entry and .vtable_inherit directives that were
>> needed for versions of GCC prior to gcc-3.0 (when the generic C++
>> ABI was adopted) are now considered obsolete. They are now deprecated
>> diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
>> index 9632a5b2a01..587c3588b09 100644
>> --- a/gas/config/tc-aarch64.c
>> +++ b/gas/config/tc-aarch64.c
>> @@ -8743,9 +8743,9 @@ programmer_friendly_fixup (aarch64_instruction *instr)
>> /* Check for loads and stores that will cause unpredictable behavior. */
>>
>> static void
>> -warn_unpredictable_ldst (aarch64_instruction *instr, char *str)
>> +warn_unpredictable_ldst (const aarch64_instruction *instr, const char *str)
>> {
>> - aarch64_inst *base = &instr->base;
>> + const aarch64_inst *base = &instr->base;
>> const aarch64_opcode *opcode = base->opcode;
>> const aarch64_opnd_info *opnds = base->operands;
>> switch (opcode->iclass)
>> @@ -8841,6 +8841,25 @@ warn_unpredictable_ldst (aarch64_instruction *instr, char *str)
>> }
>> }
>>
>> +static void
>> +warn_deprecated (const aarch64_instruction *instr, const char *str)
>> +{
>> + const aarch64_inst *base = &instr->base;
>> + const aarch64_opcode *opcode = base->opcode;
>> + if (!(opcode->flags & F_DEPRECATED_INSN))
>> + return;
>> + switch (opcode->iclass)
>> + {
>> + case tme:
>> + as_warn (_("the TME feature has been deprecated -- `%s'"), str);
>> + break;
>> + default:
>> + /* Instruction marked as deprecated, but a suitable warning not
>> + added above. */
>> + abort();
>> + }
>> +}
>> +
>> static void
>> force_automatic_sequence_close (void)
>> {
>> @@ -9019,6 +9038,7 @@ md_assemble (char *str)
>> }
>>
>> warn_unpredictable_ldst (&inst, str);
>> + warn_deprecated (&inst, str);
>>
>> if (inst.reloc.type == BFD_RELOC_UNUSED
>> || !inst.reloc.need_libopcodes_p)
>> diff --git a/gas/testsuite/gas/aarch64/tme-warn.l b/gas/testsuite/gas/aarch64/tme-warn.l
>> new file mode 100644
>> index 00000000000..ed26e4ed95c
>> --- /dev/null
>> +++ b/gas/testsuite/gas/aarch64/tme-warn.l
>> @@ -0,0 +1,15 @@
>> +[^:]*: Assembler messages:
>> +.*: Warning: the TME feature has been deprecated -- `tstart x0'
>> +.*: Warning: the TME feature has been deprecated -- `tstart X0'
>> +.*: Warning: the TME feature has been deprecated -- `tstart x15'
>> +.*: Warning: the TME feature has been deprecated -- `tstart X15'
>> +.*: Warning: the TME feature has been deprecated -- `tstart x30'
>> +.*: Warning: the TME feature has been deprecated -- `tstart X30'
>> +.*: Warning: the TME feature has been deprecated -- `tcommit'
>> +.*: Warning: the TME feature has been deprecated -- `tcommit'
>> +.*: Warning: the TME feature has been deprecated -- `ttest x0'
>> +.*: Warning: the TME feature has been deprecated -- `ttest X30'
>> +.*: Warning: the TME feature has been deprecated -- `tcancel 0'
>> +.*: Warning: the TME feature has been deprecated -- `tcancel 65535'
>> +.*: Warning: the TME feature has been deprecated -- `tcancel 0xffff'
>> +.*: Warning: the TME feature has been deprecated -- `tcancel 0XA'
>> diff --git a/gas/testsuite/gas/aarch64/tme.d b/gas/testsuite/gas/aarch64/tme.d
>> index 24d34ea9561..66527b03921 100644
>> --- a/gas/testsuite/gas/aarch64/tme.d
>> +++ b/gas/testsuite/gas/aarch64/tme.d
>> @@ -1,4 +1,5 @@
>> #as: -march=armv8-a+tme
>> +#warning_output: tme-warn.l
>> #objdump: -dr
>>
>> .* file format .*
>> diff --git a/include/opcode/aarch64.h b/include/opcode/aarch64.h
>> index f51045210c9..2d8514b8e7d 100644
>> --- a/include/opcode/aarch64.h
>> +++ b/include/opcode/aarch64.h
>> @@ -1219,6 +1219,7 @@ enum aarch64_insn_class
>> sve_shift_tsz_bhsd,
>> sve_size_tsz_bhs,
>> testbranch,
>> + tme,
>> cryptosm3,
>> cryptosm4,
>> dotproduct,
>> @@ -1479,7 +1480,8 @@ extern const aarch64_opcode aarch64_opcode_table[];
>> #define F_OD(X) (((X) & 0x7) << 24)
>> /* Instruction has the field of 'sz'. */
>> #define F_LSE_SZ (1 << 27)
>> -
>> +/* The instruction has been deprecated. */
>> +#define F_DEPRECATED_INSN (1 << 28)
>>
>> #define F_SYS_READ (1ULL << 29)
>> /* This system instruction is used to write system registers. */
>> @@ -1542,7 +1544,7 @@ extern const aarch64_opcode aarch64_opcode_table[];
>> /* As above, plus PN registers. */
>> #define F_INVALID_IMM_SYMS_3 (3ULL << 42)
>>
>> -/* Next bit is 44, and 28 is also unused. */
>> +/* Next bit is 44. */
>>
>> /* Instruction constraints. */
>> /* This instruction has a predication constraint on the instruction at PC+4. */
>> diff --git a/opcodes/aarch64-tbl.h b/opcodes/aarch64-tbl.h
>> index 518109ecfd6..c6cb5257008 100644
>> --- a/opcodes/aarch64-tbl.h
>> +++ b/opcodes/aarch64-tbl.h
>> @@ -3374,7 +3374,7 @@ static const aarch64_feature_set aarch64_feature_mpamv2 =
>> #define MEMTAG_INSN(NAME,OPCODE,MASK,CLASS,OPS,QUALS,FLAGS) \
>> { NAME, OPCODE, MASK, CLASS, 0, MEMTAG, OPS, QUALS, FLAGS | F_INVALID_IMM_SYMS_1, 0, 0, NULL }
>> #define _TME_INSN(NAME,OPCODE,MASK,CLASS,OP,OPS,QUALS,FLAGS) \
>> - { NAME, OPCODE, MASK, CLASS, OP, TME, OPS, QUALS, FLAGS | F_INVALID_IMM_SYMS_1, 0, 0, NULL }
>> + { NAME, OPCODE, MASK, CLASS, OP, TME, OPS, QUALS, FLAGS | F_INVALID_IMM_SYMS_1 | F_DEPRECATED_INSN, 0, 0, NULL }
>> #define SVE2_INSN(NAME,OPCODE,MASK,CLASS,OP,OPS,QUALS,FLAGS,TIED) \
>> { NAME, OPCODE, MASK, CLASS, OP, SVE2, OPS, QUALS, \
>> FLAGS | F_INVALID_IMM_SYMS_2, 0, TIED, NULL }
>> @@ -5154,10 +5154,10 @@ const struct aarch64_opcode aarch64_opcode_table[] =
>> CORE_INSN ("adr", 0x10000000, 0x9f000000, pcreladdr, 0, OP2 (Rd, ADDR_PCREL21), QL_ADRP, 0),
>> CORE_INSN ("adrp", 0x90000000, 0x9f000000, pcreladdr, 0, OP2 (Rd, ADDR_ADRP), QL_ADRP, 0),
>> /* TME Instructions. */
>> - _TME_INSN ("tstart", 0xd5233060, 0xffffffe0, 0, 0, OP1 (Rd), QL_I1X, 0),
>> - _TME_INSN ("tcommit", 0xd503307f, 0xffffffff, 0, 0, OP0 (), QL_0, 0),
>> - _TME_INSN ("ttest", 0xd5233160, 0xffffffe0, 0, 0, OP1 (Rd), QL_I1X, 0),
>> - _TME_INSN ("tcancel", 0xd4600000, 0xffe0001f, 0, 0, OP1 (TME_UIMM16), QL_IMM_NIL, 0),
>> + _TME_INSN ("tstart", 0xd5233060, 0xffffffe0, tme, 0, OP1 (Rd), QL_I1X, 0),
>> + _TME_INSN ("tcommit", 0xd503307f, 0xffffffff, tme, 0, OP0 (), QL_0, 0),
>> + _TME_INSN ("ttest", 0xd5233160, 0xffffffe0, tme, 0, OP1 (Rd), QL_I1X, 0),
>> + _TME_INSN ("tcancel", 0xd4600000, 0xffe0001f, tme, 0, OP1 (TME_UIMM16), QL_IMM_NIL, 0),
>> /* SME instructions (aliases for MSR <sysreg> operations. */
>> SME_INSN ("smstart", 0xd503477f, 0xffffffff, sme_start, 0, OP0 (), QL_0, F_SYS_WRITE, 0),
>> SME_INSN ("smstop", 0xd503467f, 0xffffffff, sme_stop, 0, OP0 (), QL_0, F_SYS_WRITE, 0),
>> --
>> 2.43.0
>>
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